A virus stole the gene coding for the poison of black widow spiders, scientists have found.
The WO virus infects bacteria – and is harmless to animals – yet it possesses genes that are closely related to ones found in insects and spiders.
The virus probably uses the genes to help it infiltrate animal cells to reach the bacteria.
The findings have been outlined in the journal Nature Communications.
Sarah and Seth Bordenstein from Vanderbilt University in the US analysed the genome of WO, which belongs to a group of bacteria-infecting viruses known as bacteriophages.
WO targets the bacterium known as Wolbachia, which in turn infects the cells of insects and spiders.
The virus pinched a gene that codes for latrotoxin, the poison used by black widow spiders, and the authors suggest this may enable the virus to punch holes in cell membranes.
It’s a possible way for the virus to enter and exit the cells of eukaryotes (the domain of life comprising animals, plants and fungi).
The finding is unusual because viruses that infect eukaryotes usually co-opt eukaryote genes and viruses that infect bacteria usually assimilate bacterial genes to infect and propagate within their hosts.
But the authors of the study note that WO has to contend with the defence mechanisms of two separate domains of life – perhaps explaining why it has lifted multiple genes from eukaryotes.
During its life cycle, the WO virus is exposed to the internal environment of insect and spider cells and the scientists found other genes in its DNA that may help the virus evade animal immune systems.